Pathology case of the month. Swamp-related wound infection. Aeromonas hydrophila

A 38 year-old woman with no significant past medical history was brought to the emergency department following a motor vehicle rollover and submersion into swampy waters alongside a Louisiana interstate. In addition to multiple blunt force injuries, she suffered a laceration injury over the right lower extremity, which initially required irrigation and sterile dressing. On hospital day two, the wound became grossly infected. The wound was swabbed for culture and Gram stain, and the patient was empirically started on intravenous Piperacillin/tazobactam. Results from the Gram stain showed few white blood cells and numerous Gram negative rods. The following day, the wound continued to drain purulent material but with a stable zone of erythema. The wound was drained and debrided. On hospital day four, the blood agar plate, previously inoculated with the wound culture, grew the colonies shown in the below photograph.